Electrochemical sensors are useful in chemistry and medicine to determine the presence or concentration of a biological analyte. Such sensors are useful, for example, to monitor glucose in diabetic patients and lactate during critical care events.
Diabetes mellitus is a disorder in which the pancreas cannot create sufficient insulin (Type I or insulin dependent) or in which insulin is not effective (Type 2 or non-insulin dependent). In the diabetic state, the victim suffers from high blood sugar, which causes an array of physiological derangements (e.g., kidney failure, skin ulcers, or bleeding into the vitreous of the eye) associated with the deterioration of small blood vessels. A hypoglycemic reaction (i.e., low blood sugar) can be induced by an inadvertent overdose of insulin, or after a normal dose of insulin or glucose-lowering agent, accompanied by extraordinary exercise or insufficient food intake.
The standard of care for a diabetic person involves measuring with a self-monitoring blood glucose (SMBG) monitor, which typically entails uncomfortable finger pricks. Due to the lack of comfort and convenience, a person with diabetes will often only measure his or her glucose level only two to four times per day when using a conventional SMBG monitor. Unfortunately, these time intervals may be spread so far apart such that the diabetic may find out too late of a hyperglycemic or hypoglycemic event, thereby potentially incurring dangerous side effects. Even if a diabetic manages to take a timely SMBG value, the diabetic may still not know whether his or her blood glucose value is increasing or decreasing based on conventional methods.
Heretofore, many implantable glucose sensors often suffer from complications within the body and provide only short-term or less-than-accurate measurement of blood glucose. Similarly, conventional transdermal sensors can have problems in accurately measuring and reporting back glucose values continuously over extended periods of time.